Revision: Metallurgy Science and Technology 1 SSC (English Medium) 10th Standard Maharashtra State Board

Metals are reactive. They lose electrons easily and become positively charged ions. That is why metals are called electropositive elements.

Nonmetals are called electronegative elements because they form negatively charged ions by accepting electrons.

The compounds formed from two units, namely cation and anion are called ionic compounds.

The force of attraction between cation and anion is called as the ionic bond.

The science and technology regarding the extraction of metals from ores and their purification for the use is called metallurgy.

The process of separating gangue from the ores is called concentration of ores.

The substance added to get rid of gangue in the extraction of metal is called flux.

Most of the elements occur in nature as in combined state as minerals. The chemical composition of minerals is fixed.

Minerals from which metals can be extracted profitably are known as ores.

If minerals contain a very high percentage of a particular metal and the metal can be profitably extracted from it. These minerals are called ores.

If an ore is a carbonate or a hydrated oxide, it is heated in the absence of air to a temperature that is high but insufficient to melt the ore. The process is known as calcination.

The impurities (sand, silt, soil, gravel, etc.) present in the ore are called gangue.

Roasting is the process of heating concentrated ore to a high temperature in the presence of air. The process is usually carried out for sulphide ores.

The product obtained by the combination of gangue with flux is called slag.

Refining is the process by which crude metal is purified.

Corrosion is the gradual damage of metals caused by their reaction with components of the atmosphere, such as oxygen and moisture.

\[\mathrm{C}\mathrm{l}_2(\mathrm{g})+\mathrm{H}_2\mathrm{O}(\mathrm{l})\longrightarrow\mathrm{H}\mathrm{O}\mathrm{C}\mathrm{l}(\mathrm{a}\mathrm{q})+\mathrm{H}\mathrm{C}\mathrm{l}(\mathrm{a}\mathrm{q})\]

Nonmetals usually don’t react with water, except halogens like chlorine.

\[\mathrm{Cl}_{2}(\mathrm{g})+2\mathrm{HBr}\left(\mathrm{aq}\right)\longrightarrow2\mathrm{HCl}(\mathrm{aq})+\mathrm{Br}_{2}(\mathrm{aq})\]

Nonmetals usually don’t react with dilute acids, but halogens like chlorine do.

\[\mathrm{S}+\mathrm{H}_2\longrightarrow\mathrm{H}_2\mathrm{S}\]

\[\mathrm{N}_2+3\mathrm{H}_2\longrightarrow2\mathrm{NH}_3\]

Nonmetals react with hydrogen in special conditions.

\[\mathrm{C}+\mathrm{O}_2\xrightarrow{\text{Complete combustion}}\mathrm{CO}_2\mathrm{(Acidic)}\]

\[2\mathrm{C}+\mathrm{O}_2\xrightarrow{\text{Partial Combustion}}2\mathrm{CO~(Neutral)}\]

\[\mathrm{S}+\mathrm{O}_2\xrightarrow{\text{Combustion}}\mathrm{SO}_2\mathrm{(Acidic)}\]

Nonmetals form acidic or neutral oxides with oxygen.

• Metals are mostly solids at room temperature; mercury and gallium are exceptions and exist in liquid form.
• Metals have a shining surface called metallic lustre, which may decrease due to oxidation or reaction with gases.
• Malleability allows metals to be beaten into thin sheets (gold and silver are highly malleable), and ductility allows them to be drawn into wires (gold is the most ductile).
• Metals are good conductors of heat and electricity, with silver and copper being excellent conductors.
• Most metals are hard with high melting and boiling points, but alkali metals (sodium, potassium) are soft and low‑melting, and metals are sonorous, producing sound when struck.

• Most metals are solids at room temperature, but mercury is a liquid, and gallium and caesium melt in the palm of the hand due to their very low melting points.
• Alkali metals (lithium, sodium, potassium) are soft, low-density metals with low melting points, unlike most metals.
• Iodine, though a non-metal, shows a metallic lustre, which is unusual for a non-metal.
• Carbon exists in allotropes: diamond is the hardest natural substance, and graphite is a good conductor of electricity.
• Nonmetals are usually non-lustrous, soft, poor conductors, and exist in solid or gas states, with bromine being the only liquid non-metal.

• Most metals form basic oxides with oxygen; aluminium and zinc oxides are amphoteric.
• Reactivity with oxygen varies; sodium and potassium react quickly and are kept in kerosene.
• Metals may react with water to form hydroxides and release hydrogen gas, depending on temperature.
• Metals react with dilute acids to give salt and hydrogen gas; copper and nitric acid are exceptions.
• More reactive metals can displace less reactive ones; this forms the basis of the reactivity series.

• Metals react with oxygen to form metal oxides; some oxides dissolve in water to form alkalis (e.g., Na₂O → NaOH, MgO → Mg(OH)₂).
• Highly reactive metals like sodium and potassium react vigorously with water, producing hydrogen gas and heat, while calcium reacts slowly.
• Aluminium, iron, and zinc do not react with cold water but react with steam to form metal oxides and hydrogen gas.
• Reactive metals react with dilute acids (HCl, H₂SO₄) to form metal salts and hydrogen gas, showing different reactivity levels (Mg > Al > Zn > Fe).
• A more reactive metal displaces a less reactive metal from its salt solution, indicating a displacement reaction; noble metals like gold and platinum react only with aqua regia.

• Displacement reactions help compare metal reactivity better than reactions with water, oxygen, or acids.
• If one metal displaces another from its salt, it is more reactive (e.g., iron > copper).
• The reactivity series arranges metals from most to least reactive.
• Metals are grouped into highly, moderately, or less reactive categories.
• Metals lose electrons; nonmetals gain electrons to form ionic compounds like NaCl and MgCl₂.

• Ionic compounds are made of positive and negative ions held by electrostatic force.
• They are neutral overall as charges of ions balance each other.
• They are hard, brittle, and crystalline due to a regular ion arrangement.
• They have high melting and boiling points because of the strong attraction between ions.
• They dissolve in water and conduct electricity when molten or in solution, but not when solid.

• Reactive metals occur in combined form (as oxides, sulphides, etc.), while unreactive metals like gold and silver occur in the free state.
• Minerals are natural metal compounds; those from which metals can be extracted economically are called ores, and impurities present in ores are called gangue.
• The complete process of extracting and purifying metals from ores is called metallurgy.

• Refining means purifying a crude metal by removing impurities.
• Distillation is used for metals such as zinc and mercury, which have low boiling points.
• Liquation is used for soft metals such as lead and tin, which have low melting points.
• Electrorefining uses electricity to purify metals like copper and silver.
• Pure metal collects at the cathode; impurities settle as anode mud.